The use of ultralight materials for construction of weight supporting orthosis will be applied to a group of infants with osteogenesis imperfecta Osteogenesis imperfecta patients between 9 and 18 months of age will be randomly assigned to standard medical/rehabilitation/orthopedic management or experimental bracing, vigorous rehabilitation therapy in hospital in order to determine the effects of early weight bearing on musculoskeletal development in osteogenesis imperfecta. Comparison between standard and more radical therapy will be made q 8 months for 10 years. No patients have been entered into the protocol to date.